外源亚精胺对NaCl胁迫下毕氏海蓬子光合参数和叶绿体超微结构的影响

Effects of exogenous spermidine on photosynthetic parameters and chloroplast ultrastructure of Salicornia bigelovii under NaCl stress

在0、100、300、500和700 mmol.L-1NaCl胁迫条件下比较了喷施0.1 mmol.L-1亚精胺(Spd)对毕氏海蓬子(Salicornia bigelovii Torr.)幼苗叶绿素含量、净光合速率、气孔导度、胞间CO2浓度和叶绿体超微结构的影响。结果表明:毕氏海蓬子的叶绿素含量、净光合速率和气孔导度均呈低浓度条件下(0、100和300 mmol.L-1NaCl)升高、高浓度条件下(500和700 mmol.L-1NaCl)降低的趋势,在300 mmol.L-1NaCl胁迫条件下达到最高值;胞间CO2浓度则呈低浓度NaCl胁迫条件下降低、500 mmol.L-1NaCl条件下升高、700 mmol.L-1NaCl条件下略降低的趋势;在0～500 mmol.L-1NaCl胁迫条件下叶绿素a/b值变化不明显,但在700 mmol.L-1NaCl条件下急剧降低。在低浓度NaCl胁迫条件下,叶绿体整体膨胀,类囊体片层结构松散,但叶绿体和类囊体结构仍保持完整;而经500和700 mmol.L-1NaCl处理后,叶绿体超微结构被严重破坏,叶绿体膜结构破裂、类囊体结构松散呈放射状、有些叶绿体完全解体。而在相应的NaCl胁迫条件下喷施0.1 mmol.L-1Spd,毕氏海蓬子的叶绿素含量、净光合速率、气孔导度和胞间CO2浓度虽然也呈现出相同的变化趋势,但其数值均显著高于对照(未喷施Spd);且叶绿体超微结构的损伤程度也轻于对照。研究结果说明:喷施外源Spd能够减缓NaCl胁迫对毕氏海蓬子的伤害作用。

Under 0, 100, 300, 500 and 700 mmol.L-1 NaCI stress, effects of spraying 0.1 mmol. L-1 spermidine （Spd） on chlorophyll content, net photosynthetic rate, stomatal conductance, intercellular CO2 concentration and chloroplast ultrastructure of Stlicornia bigelovii Tort. seedling were compared. The results show that chlorophyll content, net photosynthetic rate and stomatal conductance of S. bigelii all appear the trend of increasing under low concentration condition （0, 100 and 300 mmol. L-1NaC1） and decreasing under high concentration condition （500 and 700 mmol. L-1 NaC1） with the highest value under 300 mmol. L-1 NaC1 stress. While intercellular CO2 concentration appears the trend of decreasing under low concentration NaC1 stress, increasing under 500 mmol. L-I NaC1 stress and slightly decreasing under 700 mmol . L-1NaC1 stress. Under 0-500 mmol. L-1NaC1 stress, Chla/Chlb value has an un- obvious change, but sharply decreases under 700 mmol. L-1NaC1 stress. Under low concentration NaC1 stress, chloroplast overall swells and thylakoid lamella loosens but structures of chloroplast and thvlakoidstill remain intact. While under 500 and 700 mmol . L-1 NaC1 stress, chloroplast ultrastructure is damaged seriously with membrane structure rupturing and thylakoid loosening to radial, and some chloroplasts completely disaggregate. After spraying 0.1 mmol . L-1 Spd under corresponding NaC1 stress, though chlorophyll content, net photosynthetic rate, stomatal conductance and intercellular CO2 concentration of S. bigelovii also appear the same change trend, but their values all are significantly higher than those of the control （ not spraying Spd） and the damage of chloroplast ultrastructure is also lighter than that of the control. It is suggested that spraying exogenous Spd can alleviate the injury of NaCl stress to S. bigelovii.